The field of invention relates generally to supports for substrates. More particularly, the present invention is directed to a chuck suited for use in imprint lithography.
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication have been employed include biotechnology, optical technology, mechanical systems and the like. Many of the micro-fabrication techniques involve various processes, including deposition, such as chemical vapor deposition, physical vapor deposition, atomic layer deposition and the like, as well as wet and/or dry etching techniques to pattern substrates.
In addition to the standard micro-fabrication techniques, there exists a relatively new and efficient patterning technique referred to as imprint lithography. An exemplary imprint lithography is described in detail in numerous publications, such as U.S. Pat. No. 6,873,087 entitled HIGH PRECISION ORIENTATION ALIGNMENT AND GAP CONTROL STAGES FOR IMPRINT LITHOGRAPHY PROCESSES; U.S. Pat. No. 6,842,226, entitled IMPRINT LITHOGRAPHY TEMPLATE COMPRISING ALIGNMENT MARKS; U.S. Pat. No. 6,696,220 entitled TEMPLATE FOR ROOM TEMPERATURE, LOW PRESSURE MICRO-AND NANO-IMPRINT LITHOGRAPHY; and U.S. Pat. No. 6,719,915 entitled STEP AND FLASH IMPRINT LITHOGRAPHY, all of which are assigned to the assignee of the present invention. The fundamental imprint lithography technique as shown in each of the aforementioned published patent applications includes formatting a relief pattern in a polymerizable layer and transferring the relief pattern into an underlying substrate to form a relief image in the substrate. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified forming a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The substrate and the solidified layer are then subjected to processes to transfer into the substrate a relief image that corresponds to the pattern in the solidified layer.
As a result of the aforementioned micro-fabrication techniques, the demand to ensure the flatness/planarity of substrates being processed/patterned has increased. Typically, it is desired that the substrate flatness be greater than the depth of focus requirements of the process for typical photolithographic patterning techniques. The depth of focus is determined by the wavelength of light, numerical aperture of lenses and other considerations of the lithography equipment, as well as the post imaging processes. As a result, it is often desired that the substrate flatness be such that the variation in height of the region being patterned be no greater than 200 nm. This has proved challenging, because substrates having a planarization layer disposed thereon demonstrate height variations over an area of the planarization layer being processed that is on the order of microns.
Most prior art chucking systems attempt to abrogate the non-planarity of substrates employing vacuum and/or electrostatic forces. Although this reduces the warp and bow in the substrate over the entire area of the same, these systems often are unable to attenuate local height variations. In addition, the presence of back-side particles exacerbates non-planarity problems of substrate.
There is a need, therefore, to provide improved support systems for substrates.